Demonstrate config diff in simple consumer

integrations/ckconfig/examples/simple/main_test.go

@@ -0,0 +1,81 @@
+package main
+
+import (
+	"bytes"
+	"context"
+	"io"
+	"testing"
+
+	commandkit "gitea.maximumdirect.net/eric/CommandKit"
+	"gitea.maximumdirect.net/eric/CommandKit/integrations/ckconfig"
+	"go.yaml.in/yaml/v4"
+)
+
+func TestSimpleAppComparesFixturesAndKeepsDefaultCommands(t *testing.T) {
+	app, err := newApp()
+	if err != nil {
+		t.Fatal(err)
+	}
+	var output bytes.Buffer
+	outcome := app.Execute(context.Background(), []string{"config", "diff", "--config", "fixtures/before.yml", "--against-config", "fixtures/after.yml"}, commandkit.Streams{Out: &output, Err: io.Discard})
+	if outcome.Kind != commandkit.OutcomeSuccess {
+		t.Fatalf("fixture comparison outcome = %#v", outcome)
+	}
+	var report yaml.Node
+	if err := yaml.Unmarshal(output.Bytes(), &report); err != nil {
+		t.Fatalf("comparison report is not YAML: %q: %v", output.String(), err)
+	}
+	changes := field(report.Content[0], "changes")
+	greeting := field(changes, "greeting")
+	if greeting == nil || greeting.Value != "Goodbye" {
+		t.Fatalf("fixture comparison report = %q", output.String())
+	}
+
+	output.Reset()
+	outcome = app.Execute(context.Background(), []string{"config", "diff", "--config", "fixtures/before.yml", "--against-config", "fixtures/before.yml"}, commandkit.Streams{Out: &output, Err: io.Discard})
+	if outcome.Kind != commandkit.OutcomeSuccess {
+		t.Fatalf("equal fixture comparison outcome = %#v", outcome)
+	}
+	if reportNode, err := decodeReport(output.Bytes()); err != nil || len(field(reportNode, "additions").Content) != 0 || len(field(reportNode, "changes").Content) != 0 || len(field(reportNode, "deletions").Content) != 0 {
+		t.Fatalf("equal fixture report = %q, decode error %v", output.String(), err)
+	}
+
+	output.Reset()
+	outcome = app.Execute(context.Background(), []string{"config", "show"}, commandkit.Streams{Out: &output, Err: io.Discard})
+	if outcome.Kind != commandkit.OutcomeSuccess || output.String() != "greeting: Hello\n" {
+		t.Fatalf("default show outcome/output = %#v / %q", outcome, output.String())
+	}
+
+	output.Reset()
+	outcome = app.Execute(context.Background(), []string{"greet"}, commandkit.Streams{Out: &output, Err: io.Discard})
+	if outcome.Kind != commandkit.OutcomeSuccess || len(output.String()) == 0 || output.String()[:5] != "Hello" {
+		t.Fatalf("default greeting outcome/output = %#v / %q", outcome, output.String())
+	}
+}
+
+func TestSimpleLoaderDoesNotReplaceExplicitEmptyConfiguration(t *testing.T) {
+	_, err := loadAppConfiguration(context.Background(), ckconfig.Selection{Config: commandkit.Supplied[string]{Set: true}})
+	if err == nil {
+		t.Fatal("explicit empty configuration fell back to the default source")
+	}
+}
+
+func field(mapping *yaml.Node, name string) *yaml.Node {
+	if mapping == nil || mapping.Kind != yaml.MappingNode {
+		return nil
+	}
+	for index := 0; index+1 < len(mapping.Content); index += 2 {
+		if mapping.Content[index].Value == name {
+			return mapping.Content[index+1]
+		}
+	}
+	return nil
+}
+
+func decodeReport(data []byte) (*yaml.Node, error) {
+	var document yaml.Node
+	if err := yaml.Unmarshal(data, &document); err != nil {
+		return nil, err
+	}
+	return document.Content[0], nil
+}